avoid hang on overflow boxes that syphon water to a sump they are very very unreliable.theres alot of places that will drill glass for you and its very easy to do your self as well and the bits can be got at princess auot for cheap.you dont need to get a tank custom made as most tanks on here are drilled anyways.just post an ad with the dimensions you are looking for and ask if anyone has one for sale or if anyone wants to build one for you.a tank that size should cost you less than $100 second hand but if you get it made it would cost more depending on the style of overflow you choose and type of glass work
any advice jerry and feel free to ask its what were all here for